DR WAQAS NAWAZ PMAS Arid Agriculture University, Rawalpindi Pakistan

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“It is a disease of horses caused by RNA virus of the genus Arterivirus”
Etiology:
It is a viral disease
Family-----Arteriviridae
Genus-------Arterivirus
Species------ Equine arteritis virus (EAV)
Porcine reproductive & respiratory syndrome virus (PRRSV)
Lactose dehydrogenase elevating virus (LDV)  mice
 Genome: RNA virus, small, enveloped, icosahedral core with +ve sense RNA genome
 Resistance/Viability:
o Inactivated at 56-58°C for 20-30 mint
o Remain viable for 2-3 days at 37-38°C
o For up to 75 days at 4-8°C
History:
 EAV was First isolated from horses in Ohio (state of USA) in 1953
 It is known that some breeds of horses in USA are more prone to it but there is no breed
immunity
 In UK, it is notifiable disease
 There is no known human health hazard
Epidemiology:
 Antibodies to EAV have been found in most of the countries where the testing has been
done.
 Sero +ve horses have been reported in South & North America, Europe, Asia, Africa &
Australia. Iceland & Japan are EAvirus-free
 First outbreak of EVA was seen in UK in 1993. Affected 6 premises & around 100 horses
were affected.
Transmission:
Most frequent route of transmission is respiratory system but virus can also be spread by vinereal
route including artificial insemination. Stallions may become carrier & can become carrier for
long term & transmit it during breeding. Virus can be transmitted on fomites including
equipments & may be spread mechanically by human or animals. Incubation period = 2-14 days
Synonymous:
 Equine typhoid
 Pink eye

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Sign & Symptoms:
Infected horses show variable symptoms including;
Fever (peaking up to 41°C)
Nasal discharge
Depression
Edema
Conjunctivitis or “Pink eye”
Abortion in pregnant mares
Swelling in limbs & genital areas in both mare & stallion
Signs vary with age, more severe in young but less in adults. The clinical signs are
generally more severe in old & very young horses or the animals that are immune-suppressed or
in poor condition.
There is interstitial pneumonia and/or arteritis can be seen in foals up to few months of
age. Systemic illness also occurs in adults. In adult horses, the clinical signs include;
 Fever
 Depression
 Limb edema (hind limb particularly)
 Edema of the dependant portion including ventral body wall
 Conjunctivitis
 Photophobia
 Peri-orbital edema
 Supra-orbital edema
 Rhinitis
 Abortion or still birth can occur in mares that are pregnant when they are exposed.
Postmortem Findings/Lesions:
In Acute Cases In Foals
Edema, congestion & hemorrhages of the S/C
tissue, visceral organs & the lymph nodes
Pulmonary edema
Interstitial pneumonia
Emphysema
Enteritis
Morbidity & Mortality:
In US, the survey was conducted in 1998, this infection is more common among the
standardbreds. Followings were having the antibodies to that virus;
 24% of unvaccinated Standardbreds
 3.6% of Warmblood horses & 4.5% of Thoroughbreds

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This variation among breeds may be due to genetic factors but they are more likely to be
caused by different management practices because 10-70% of different carriers were from the
same area. Abortion rate = less than 10 to 50-60% (10-50%)
Differential Diagnosis:
Equine infectious anemia
Equine influenza
African horse sickness
Some bacterial infections i.e streptococcus infections
Poisoning from toxic plants
Diagnosis:
 First line of diagnosis is the isolation of virus directly
 Detection of viral antigen
 Serology  very important in carrier stage to be detected i.e ELISA, CFT, VNT
 RT-PCR (Reverse Transcription PCR)
 Virus can be isolated in rabbits, equine & monkey kidney cells & cell lines. RK-13 cells
are the system of choice. (RK means Rabbit Kidney) (FMD = BHK-21, PPR = VERO)
 Carriers can also be detected by breeding the stallion to 2 seronegative mares which are
checked for seroconversion four weeks after breeding.
 Serology is also helpful in surveillance and to confirm the absence of infection before
vaccination.
Control:
Acutely infected horses should be isolated to prevent transmission in secretions and
excretions. Precautions should also be taken to avoid spreading the virus on fomites. EAV is
readily inactivated by detergents, common disinfectants and lipid solvents.
Treatment:
No specific treatment is available; however, most healthy horses other than young foals
recover on their own. Good nursing and symptomatic treatment should be used in severe cases.
Vaccination can also help contain outbreaks. Venereal transmission can be controlled by good
management and vaccination. To protect pregnant mares from abortion, they should be separated
from other horses and maintained in small groups according to their predicted foaling dates.
Newly acquired horses should be isolated for 3 to 4 weeks before mixing with the old flock at
farm. Carriers should be housed where they can be physically separated from unvaccinated
horses. Breed them with healthy horses. This is not zoonotic.

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Steps:
1. Denaturation
2. Annealing
3. Extension
Reverse transcriptase PCR (RT-PCR)
It is for RNA Viruses
Conventional RT-PCR Real Time RT-PCR
RT-PCR rRT-PCR
Two step RT-PCR One step RT-PCR
1st the RNA converts into cDNA
2nd
the cDNA enters the PCR process
In this method, as we insert the sample,
computer screen will show the lines of PCR
4-5 hour 10-12 hours
One step = RNA  PCR
Two step = RNA  cDNA  PCR